[ImportVerilog] Allow functions to capture values from parent scope #9107
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fabianschuiki
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Oct 17, 2025
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Really cool! LGTM!
This patch teaches the ImportVerilog conversion to detect and plumb captured
references from enclosing scopes into lowered MLIR functions.
- **FunctionLowering**
- Added `captures` and `captureIndex` to record refs captured from outer
scopes.
- **Context**
- Added `finalizeFunctionBodyCaptures` to extend the function signature with
captured `moore::RefType` inputs and replace their in-body uses with the
new block arguments.
- `convertFunction` now installs a temporary `rvalueReadCallback` that
collects refs read from outside the function’s body.
- **Expressions**
- When lowering subroutine calls, the visitor now appends any captured
operands to the call argument list. Captures are verified to be
`moore::RefType` values originating from the enclosing (module) region.
Together these changes allow nested or free functions to reference module-level
signals (`logic`, etc.) correctly in the generated MLIR, with explicit
function parameters modeling captured variables.
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This patch teaches the ImportVerilog conversion to detect and plumb captured references from enclosing scopes into lowered MLIR functions.
capturesandcaptureIndexto record refs captured from outer scopes.finalizeFunctionBodyCapturesto extend the function signature with capturedmoore::RefTypeinputs and replace their in-body uses with the new block arguments.convertFunctionnow installs a temporaryrvalueReadCallbackthat collects refs read from outside the function’s body.moore::RefTypevalues originating from the enclosing (module) region.Together these changes allow nested or free functions to reference module-level signals (
logic, etc.) correctly in the generated MLIR, with explicit function parameters modeling captured variables.